The present invention relates to a magnetic multilayer structure having both characteristics of a high saturation magnetic flux density and a high relative permeability. This magnetic multilayer structure is suitable for use in a magnetic pole of a magnetic head which exhibits excellent recording and reproducing characteristics to a high density magnetic recording medium with a high coercive force. However, this structure is not limited to this application.
Hitherto, a magnetic layer constituting a magnetic pole of a magnetic head for magnetic recording is made of an alloy containing Fe, Co or Ni as a main component and has a saturation magnetic flux density above 10 kG or a saturation magnetic flux density above 18 kG in the case of an Fe-Si system alloy and has been developed as a magnetic pole material of a magnetic head for high density recording (JP-A No. 59-182938). To obtain a magnetic field having a steep distribution for high density recording, it is necessary to set a thickness of the tip portion of the magnetic pole of the magnetic head or a thickness of the whole magnetic pole when it is measured in the moving direction of a recording medium to be 0.5 .mu.m or less. Since the magnetic flux density in this portion is high, it is necessary to form this portion by a material having a high saturation magnetic flux density, a high permeability, and a low coercive force. Further, since a thickness of this portion is thin, magnetic saturation occurs. Therefore, in order to realize desired recording and reproducing characteristics of a head, a high saturation magnetic flux density above 15 kG is needed to use a thickness of layer not larger than 0.5 .mu.m. On the other hand, to satisfy the recording and reproducing characteristics of the head irrespective of the above-mentioned thickness of layer, a high relative permeability above 1000 and a low coercive force below 1 Oe are needed.
Hitherto, a magnetic layer is formed by a high frequency sputtering method or the like. In the case of using a material containing Fe as a main component, the magnetic characteristic of the magnetic layer has a high saturation flux density above 15 kG. However, its relative permeability has a low value below 700. Therefore, the conventional magnetic layer is improper to form a magnetic head adapted to perform high density recording. Therefore, hitherto, it is extremely difficult to form a magnetic layer having both characteristics of a high saturation magnetic flux density and a high relative permeability.